1. Field of the Invention
The present invention relates to a sublimation transfer type thermal printer and ink ribbon used by the printer, and more particularly relates to the technique of stabilizing the print quality by making a precise control of the print density.
2. Description of the Prior Art
The sublimation transfer type thermal printer has an ability to achieve smooth and natural gradation expression, and is characterized by its excellent expressiveness, high print quality and natural image reproducibility. In this view, it is frequently used for the special purpose which requires printing of high quality and high fidelity, such as an output of printed matter for the correction, medical printings such as CT-scanner or radiograph, or color samples of products in the apparel industry or other industry. In such cases, simply printing the original image data does not satisfy the requirement of special printing quality. Therefore, in such cases, the original image data is corrected to compensate for the variation of the ink ribbon characteristics, and the corrected image data is printed.
The variation in characteristic of the ink ribbons result in the problem that an appropriate normal gradation with respect to the print density cannot be reproduced, even if the printing condition of the thermal printer is uniform. Particularly, in the color printing, all colors are reproduced by superposing the images of three primary colors (Yellow, Magenta and Cyan) or four primary colors (Y, M, C, and Black) by using the ink ribbons of those colors. Therefore, if the normal gradation reproduction is not ensured in at least one color, the color balance is broken and high fidelity reproduction may not be achieved. In this view, the gradation correction is performed. Conventionally, the manufacturer of the ink ribbon performs test printing for respective lot of the ink ribbons, measures the print density of the test printing to calculate the correction data, and sells the ink ribbon product with the correction data sheet or the like attached. The user of the ink ribbon inputs the correction data to his printing system or image processing system via keyboard or the like to make the appropriate gradation correction, before starting the printing.
However, in such a case, the user needs to input the correction data by manual operation every time when he exchange the ink ribbon, and it is very time-consuming and troublesome. Moreover, there is relatively large possibility of erroneously inputting the correction data because many correction values should be inputted.
It is an object of the present invention to provide an ink ribbon and a thermal printer in which the correction data is automatically inputted to the thermal printer by simply setting the ink ribbon to the printer.
According to one aspect of the present invention, there is provided an ink ribbon for use in a sublimation transfer type thermal printer, including: an ink ribbon body portion which is coated with color ink; and an ink ribbon head portion on which gradation correction data is recorded. According to this ink ribbon, the gradation correction data is recorded at the head portion of the ink ribbon, and therefore the gradation correction data can be read and the gradation correction can be performed prior to the actual printing.
The ink ribbon head portion may be a leader film of the ink ribbon. The correction data is obtained after the test printing by using the ink ribbon manufactured. The correction data thus obtained is recorded on the leader film and then the leader film is attached to the ink ribbon body portion, thereby simplifying the manufacturing process of the ink ribbon. According to need, the gradation correction data may be prepared, not for each manufactured lot, but for each product of the ink ribbon.
The gradation correction data may be recorded in a form of optically-readable marks, and hence the data can be read by a general optical sensor. Namely, it is not necessary to equip the thermal printer with a special sensor.
The leader film may include an aluminum deposited plastic film, and the mark may be a light absorbing or light diffusing mark recorded on the plastic film. Therefore, different gradation correction data can be recorded on the leader films in a unit of lots or respective products, and accurate correction data can be supplied to the user. In addition, the marks can be read by a general optical sensor of reflection light detection type. On the contrary, the mark may be a light intercepting mark recorded on the plastic film. In that case, the marks can be read by a general optical sensor of transmitted light detection type.
The marks may include a plurality of sub-marks arranged in a form of a matrix including sub-mark lines positioned perpendicularly to a transfer direction of the ink ribbon. The sub-mark line represents a byte or a word which is a unit gradation correction data, and the sub-mark lines are arranged in alignment with each other in a the transfer-direction. Therefore, the unit data, byte or word, can be read during the process of the ink ribbon transfer, and the byte or word can be arranged appropriately in accordance with the reading order thereof.
The gradation correction data may include a start position mark and an end position mark of the gradation correction data, and the start position mark and the end position mark include sub-mark lines in each of which all sub-marks have identical value. Therefore, the position of the marks can be readily recognized. Further, the sub-mark line may include a sub-mark for parity check bit. By this, the erroneous reading may be checked and correct reading is ensured. The sub-mark line may include a sub-mark indicating a reference timing of detecting the sub-marks. By this, the reading timing of the marks can be accurately controlled and the correct reading is ensured.
According to another aspect of the present invention, there is provided a thermal printer including: a detection unit for reading marks of gradation correction data recorded at a header portion of an ink ribbon and outputting a read-out signal; a reproduction unit for receiving the read-out signal and reproducing the gradation correction data; and a storage unit for storing the gradation correction data. In accordance with the thermal printer thus configured, the detection unit detects the gradation correction data, the reproduction unit reproduces the correction data, and the storage unit stores it. The gradation correction can be carried out by using the correction data thus stored. Since the gradation correction is applied to the original image data, not only the thermal printer but the external image processing unit may do the correction. Every time when the ink ribbon is exchanged, new correction data is stored in the thermal printer, and the stored data is retained there until new ink ribbon is set.
The thermal printer may further include: an operation unit for performing gradation correction of image data to be printed based on the gradation correction data; and a printing unit for printing the image data corrected by the operation unit. With this configuration, the thermal printer can perform the gradation correction and then do the printing.
According to still another aspect of the invention, there is provided an ink ribbon for use in a sublimation transfer type thermal printer, including: ink ribbon portions which is coated with color ink; and marks of manufacturing information recorded on the ink ribbon.
According to the ink ribbon, the manufacturing information is recorded on the ink ribbon and readable therefrom, and hence the gradation correction data corresponding to the ink ribbon can be identified based on the manufacturing information.
The marks may be recorded at a head portion of a group of the ink ribbon portions used for a single printing operation, and this enables easy reading of the manufacturing information prior to the use of group of the ink ribbon for printing. Further, the marks may be recorded on a leader film of the ink ribbon. In this case, the manufacturing information is recorded on the leader film and then it is attached to the ink ribbon, thereby simplifying the manufacturing process of the ink ribbon.
The marks may be optically readable marks so that an optical sensor of general type can read the marks. The marks may be recorded by an ink jet printer. By this, the manufacturing information can be readily recorded. Compared with recording the information by using a print form plate, it is not necessary to produce new plates every time the products of different lot is manufactured. Further, the marks may be recorded by a fusion transfer type thermal printer to record the information with high quality, thereby improving the reliability in reading the marks.
The leader film may include an aluminum deposited plastic film, and the mark may be a light absorbing or light diffusing mark recorded on the plastic film. By this, the marks can be read by a general optical sensor of reflection light detection type. Contrary, the mark may be a light intercepting mark recorded on the plastic film so that a general optical sensor of transmitted light detection type can be used. Further, the mark may be a bar-code which is established technically, is readable accurately and requires: low cost. The marks may be aligned in a transfer direction of the ink ribbon so that the manufacturing information can be readily read during the transfer of the ink ribbon. Further, the marks may include positioning marks specifying head portions of the ink ribbon portions, and the marks are recorded in alignment with the positioning marks in the transfer direction. With this structure, the marks of the manufacturing information and the positioning marks are readable by the same optical sensor.
According to still another aspect of the invention, there is provided a thermal printer including: a detection unit for reading manufacturing information recorded on an ink ribbon and outputting a read-out signal; a reproduction unit for receiving the read-out signal and reproducing the manufacturing information; and a storage unit for storing the manufacturing information. With this configuration, the detection unit detects the manufacturing information, the reproduction unit reproduces the information, and the storage unit stores it. The gradation correction can be carried out by using the correction data which is identified with the aid of the manufacturing information stored. Every time when the ink ribbon is exchanged, new correction data is stored in the thermal printer, and the stored data is retained there until new ink ribbon is set.
The thermal printer may further include: an operation unit for performing gradation correction of image data to be printed based on the manufacturing information; and a printing unit for printing the image data corrected by the operation unit. Further, the operation unit may include a database for storing a plurality of gradation correction data in association with manufacturing information; and a selecting unit for selecting the gradation correction data corresponding to the manufacturing information stored in the storage unit. With this configuration, the thermal printer can perform the gradation correction and then do the printing.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiment of the invention when read in conjunction with the accompanying drawings briefly described below.